Yuri Tatarchuk has a disconcerting way of demonstrating Chernobyl’s grim radioactive legacy. An official guide at the wrecked nuclear power plant, he waves his radiation counter at a group of abandoned Soviet army vehicles that were used in the battle to clean up the contamination created by the reactor explosion in 1986.

“Some of these trucks are quite clean, but some of them not,” he announces. A sweep of his counter reveals only a few clicks from their doors and roofs. Then he passes the device over one vehicle’s tracks. A sudden angry chatter reveals significant levels of radiation.

“Wheels and tracks pick contamination from the soil,” he tells the group that has gathered round him. “There are still plenty of radioactive isotopes – caesium, strontium, even some plutonium – in the ground and we cannot get rid of them.” Twenty-five years on, Chernobyl remains a poisoned landscape.

Set among lakes, sandy soil and forests on steppe lands north of Kiev, Chernobyl achieved global notoriety in 1986 when technicians carried out an experiment aimed at testing backup electrical supplies to one of the plant’s four reactors. The flow of water – used as a coolant to carry away the mighty heat of the reactor core – was raised and lowered.

After a few minutes, there was a sudden jump in reactor power. Ten seconds later the core was blown apart by a massive explosion.

Without a containment vessel, the reactor’s deadly radioactive contents were borne high into the air by the heat of the core’s burning graphite and spread over much of Europe, triggering an international panic.

In the blast’s immediate aftermath, 31 plant operators and firemen died – they were not told the reactor was the cause of the blaze or that radiation levels were lethal – while thousands more people, living on land that is now in Ukraine and Belarus, received doses that undoubtedly shortened their lives, although scientists still dispute the death toll. The World Health Organisation puts it at 4,000; Greenpeace says 200,000.

The Chernobyl explosion was the world’s worst nuclear accident and until recently was the only one classified as level 7 on the International Nuclear Event Scale. April 26 will mark the 25th anniversary of the blast, a birthday that has acquired a dramatic resonance following the Fukushima reactor fires in Japan, which have resurrected global fears that nuclear mayhem could afflict the planet again. The Fukushima disaster is now also classified as level 7.

Chernobyl clearly has much to tell us about the dangers of nuclear power. Hence the recent soaring interest in the plant which, bizarrely, has become a popular tourist destination for foreign visitors to Ukraine. My coach trip in March from Kiev was a sellout – with the 25-strong party including 15 members of the German, US, Russian, Dutch and British media. Television crews fought to interview the few baffled members of the public on the bus about the forthcoming anniversary, while other journalists simply interviewed each other. I was cross-examined for Russian TV about the safety of nuclear power as I stood in front of the radioactive ruins of reactor number 4.

It was an extraordinary affair led by the ebullient Tatarchuk, a chunky, cheerful Ukrainian wearing a T-shirt bearing the slogan "Hard Rock Café – Chernobyl". Sites on our strange tour included the buried village of Kopachi, a close-up look at reactor number 4 itself, a very quick drive through the Red Forest and an exploration of the abandoned city of Pripyat. Radiation counters were handed out, and if these started to chatter too quickly – usually if we wandered off paths and on to open soil – we were told to make a detour. It was startlingly casual and, in the end, highly unsettling.

The Ukrainian steppe is still frost-burned and the trees leafless at this time of year. There are no buds on branches and little hint of greenery, a combination that only enhances the eerie desolation inside the 30-kilometre exclusion zone around the reactor. This land has seen harrowing times. It was occupied by German troops and most communities have memorials to the Soviet soldiers who liberated them – including the village of Kopachi inside the zone. In fact, Kopachi’s memorial is just about all that is left of the place, thanks to Chernobyl.

“Kopachi was very badly contaminated and so it was decided to bury it, house by house,” says Tatarchuk. “It seemed a good idea at the time, but it wasn’t. The digging only pushed radioactive material deeper into the soil and closer to the water table, so that contamination spread even further.” It transpires that devastating errors like these were common.

The only other evidence of Kopachi’s existence is the primary school near the memorial. Its windows have rotted and the front door hangs on a single hinge. It is also clear that it was abandoned in haste. Schoolbooks, notebooks, sheets of music and road-safety leaflets litter the hall floor while a single doll – its face blackened and cracked – lies on a cot inside one classroom.

Equally disturbing is the vast artificial lake built near the main plant, which was used to provide water coolant for its four reactors. The lake was frozen in March, but while Chernobyl’s reactors were operating its water was warm all year round. Lichen blossomed, so a fish farm was built to populate the lake with catfish that ate the lichen and kept the waters clear.

After the reactor explosion, the lake was showered with radioactive debris which sank to the bottom. Today water has to be pumped constantly from the nearby river Pripyat to stop the lake evaporating in summer and exposing its toxic sediments, which would dry out and be spread by the wind.

However, it is Pripyat that provides the most disturbing evidence of the events of 25 years ago. The city was built to house the families of workers who manned the vast reactor complex at Chernobyl. Four reactors had been built by 1986 and two more were under construction. This was to be the biggest nuclear-power complex in Europe. Fifty thousand people had homes here.

Reactor no 4 blew up in the early hours of April 26, but no one told the people of Pripyat. All that day, children were allowed to play outside, despite the plume of radioactive material emerging from the reactor a few kilometres away.

Of course, there were rumours of a fire, but people had been indoctrinated to believe a reactor accident was impossible – until a fleet of buses arrived at 2pm the next day, 36 hours after the explosion, and Pripyat’s people were shipped off to camps and resettlement centres. At the time, they were told they would be allowed back to their homes within three days, but in the end they were never allowed to return.

For an hour, our group wandered round Pripyat, stepping over broken glass and lumps of wood and stone, with the constant chirrup of our radiation counters providing warnings if we strayed too far. Everywhere nature can be seen to be taking back its territory. Trees have erupted through the thick concrete steps of Pripyat’s central plaza, while the surrounding woods – which now provide homes for healthy populations of wolves, deer and boar – have spread over every piece of open ground.

Inside the city, books are littered over the grimy floors of the main library while outside, a Ferris wheel – set up to celebrate May Day that year – is slowly rusting.

How many people received fatal doses of radiation in those 36 hours of exposure remains a matter of dispute. Although cheery for most of the trip, Yuri Tatarchuk’s anger about the fate of the people of Pripyat at the hands of Ukraine’s former Soviet masters became all too clear: “People were told that they had received a radiation dose of no more than 25 rems, enough to cause only minor illness. But that just was not true. They must have got hundreds of rems, fatal doses.

“It was criminal. People should have been given proper diagnoses and proper treatment. They got nothing. At least 5,000 people were badly affected at the time, while women who were pregnant were simply told to have abortions. It was a cruel time.”

Today workers are allowed to live in the village of Chernobyl, but for no more than four days at a time. With all four reactors at the plant closed down, they are helping to decontaminate the land within the exclusion zone and to decommission the plant’s first three undamaged reactors. As to reactor no 4, the concrete sarcophagus that hides its wrecked, exposed, radioactive core is now crumbling and work has started on a replacement – although Ukraine has made it clear that it will need international assistance to ensure the project’s successful completion.

This is a nation that will have to bear the consequences of the world’s worst nuclear accident for a long time to come.

As to the comparison between Fukushima and Chernobyl, Tatarchuk is emphatic: “No, it is not as bad in Japan as it was here, not by a long way. But there are lots of similarities. Basically, we had high radiation and no information in 1986, and that seems to be going on once more. That is the pattern when these things happen.”

The legacy

-- The Chernobyl reactor was a class of atomic plant known as an RBMK. Of the 17 operating in 1986, only 11 – all in parts of the former Soviet Union – are still in use. Plans for another eight were scrapped and there is international pressure for those still in use to close.

-- Four hundred times more radioactive material was released at Chernobyl than at Hiroshima. The cloud of fallout spread over most of Europe, with the exception of Spain and Portugal.

-- The cost of the disaster has crippled the national budgets of Ukraine and neighbouring Belarus. In 1998, Ukraine said it had already spent US$130 billion cleaning up after the accident while Belarus said it would have to pay out US$35 billion that year alone. Vast tracts of its farm land had been ruined.

-- Dozens of farms in Britain, mainly in the north-west England’s Lake District and in northern Wales, are still restricted in the way they can use land and rear sheep because of radioactive fallout from Chernobyl.

-- Scientists say that radiation will affect the Chernobyl area for 48,000 years although it will be safe enough for humans to begin repopulating the area long before then -- in about 600 years.